Why do non-drowsy antihistamines not work as well as regular antihistamines that cause drowsiness?

If I take a nondrowsy antihistamine like Claritin it does nothing for me. If I take a regular antihistamine like Benedryl it stops my allergy symptoms, but knocks me out. Does anyone else have this problem?
Answer:
All allergy medications have different ingredients, so different ones will work better. When you choose a non-drowsy brand over a brand that causes drowsiness, you are getting a completely different medication. I get drowsy with Benadryl, too.I cannot use Claritin, Alavert, or Zyrtec because none of those work. So, here's what I do when I take Benadryl or Allegra. Along with it, I also take a vitamin B complex pill. It sounds odd, but it really works well. The B vitamins give great energy, so usually the drowsiness will not come. If it still does, I drink a Mountain Dew and it helps (caffeine).Also, do not sit down right after taking the allergy medicine. Keep active for about an hour afterwards. This will help steer off the initial drowsy phase. After that hour goes by, your allergies should be relieved, but you won't be drowsy.I have found that keeping active and standing up helps drain the sinuses much better in conjunction with the medicine as well.

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Claritin does not work for some people; however there is a prescription non-drowsy tablet called Zyrtec (pronounced: Zur-Tech) that is a highly effective antihistamine (although it made me a bit drowsy for the first day or two...after that it did not).

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